title: A CT-based Monte Carlo simulation tool for dosimetry planning and analysis.
abstract: The Los Alamos code MCNP4A (Monte Carlo N-Particle version 4A) is currently used to simulate a variety of problems ranging from nuclear reactor analysis to boron neutron capture therapy. A graphical user interface has been developed that automatically sets up the MCNP4A geometry and radiation source requirements for a three-dimensional Monte Carlo simulation using computed tomography data. The major drawback for this dosimetry system is the amount of time to obtain a statistically significant answer. A specialized patch file has been developed that optimizes photon particle transport and dose scoring within the standard MCNP4A lattice geometry. The transport modifications produce a performance increase (number of histories per minute) of approximately 4.7 based upon a 6 MV point source centered within a 30 x 30 x 30 cm3 lattice water phantom and 1 x 1 x 1 mm3 voxels. The dose scoring modifications produce a performance increase of approximately 470 based upon a tally section of greater than 1 x 10(4) lattice elements and a voxel size of 5 mm3. Homogeneous and heterogeneous benchmark calculations produce good agreement with measurements using a standard water phantom and a high- and low-density heterogeneity phantom. The dose distribution from a typical mediastinum treatment planning setup is presented for qualitative analysis and comparison versus a conventional treatment planning system.
authors.affiliation: Jonsson Comprehensive Cancer Center, Department of Radiation Oncology, University of California Los Angeles, 90024-6951, USA. demarco@radonc.ucla.edu
authors.forename: J J
authors.initials: JJ
authors.lastname: DeMarco
authors.forename: T D
authors.initials: TD
authors.lastname: Solberg
authors.forename: J B
authors.initials: JB
authors.lastname: Smathers
mesh_terms: D000465:Algorithms; D016754:Boron Neutron Capture Therapy; D003198:Computer Simulation; D006801:Humans; D008168:Lung; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D017785:Photons; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed